PURPOSE: To reduce a quantity of the hardware in an information processor, and to reduce the size of the processor, by connecting plural terminal equipments to respective circuit control parts through a terminal switching part, and providing a common terminal control part which sends a switching signal to the switching part.

CONSTITUTION: A CPU1 is connected to a bus line 3, and interruption lines IRQ from respective circuit control parts 111∼11n and a timer part 9 are connected through wired OR. The control parts 111∼11n convert parallel data from the CPU1 into series data to send out transmitted data TXD by a transmission clock from a clock selector 15; and received data EXD are converted into parallel data, which are sent out to the CPU1 through the interruption lines IRQ. Under the command of the CPU1, a terminal controller 12 applies clock selection signals A and B to the selector 15 and clock from a clock frequency division part 14 is sent out to the control parts 111∼11n. Thus, the quantity of the hardware of the information processor is reduced, data are trasmitted at an optional speed among terminal equipments 41∼42n, and the size of the device is reduced.